This application claims foreign priority to Ukraine patent application no. 2001085839 filed Aug. 20, 2001.
The invention relates to new thioxanthone compounds having utility as fluorescent dyes and processes for their manufacture.
Benzothioxanthone compounds are known as fluorescent colorants.
Dyes described in U.S. Pat. Nos. 3,828,072 and 5,280,128 have the common formula: 
However, these compounds are luminescent in the orange-red region and difficult to synthesize while using undesirable components.
In particular, 14H-anthra[2,1,9-mna]thioxanthene-14-one thioxanthone colorants have been described by Carlini et al. in Dyes and Pigments, Vol. 3 (1982), pps. 59-69. One such colorant described by Carlini is 6-methoxy-14H-anthra[2,1,9-mna]thio xanthene-14-one. It is a photostable fluorescent colorant in the red region (xcexmax=614 nM). However, this colorant has the disadvantage of being poorly soluble in organic solvents and polymer materials.
The known compounds can be prepared using the schematic diagram: 
A method for preparing intermediates for synthesis is described in U.S. Pat. No. 4,036,859, IPC C09B, 3/02, 3/04, 1977. The method is based on the schematic diagram: 
and includes the following stages:
(a) reacting of 1-aminoanthroquinone with sodium nitrite in sulfuric acid to form sulfate salt of anthroquinoyl diazonium;
(b) treatment of the diazonium salt by metakrylonitril in presence of a catalytic amount of cuprous halide in methyl alcohol to form compounds 3-(1-anthro quinoyl)-2-hydroxi-2-methylpropionitril
(c) reacting of the formed compound with potassium hydroxiyl in methyl alcohol to form a red reaction mass. This mass is then filtered of contaminants, poured on acidified water and 2-oxibenzathron is extracted. It has yellow color and melt temperature of 297-298xc2x0 C., yieldxe2x80x9481%.
A drawback of this method for making the intermediate 2-oxybenzanthrone product is utilization of methanol.
The invention relates to new chemical components of the thioxanthone series of the type 14H-anthra[2,1,9-mna]thioxanthene-14-one, in particular, 6-n-octyloxy-14H-anthra[2,1,9-mna]thioxanthene-14-one of the general formula 
wherein R1 is a straight chain alkyl group having from 6 to 22 carbon;
R2, R3 and R4 are each, independently, hydrogen or alkyl having from 1 to 4 carbon atoms, and, in particular, 6-n-octyloxy-14H-anthra(2,1,9-mna)thioxanthene-14-one.
These compounds have utility as fluorescent dyes and exhibit significant luminescence in the red spectral region (xcexmax=615 nM).
The compounds are well soluble in organic solvents and exhibit intense luminescence in solvents with various polarity.
These properties of claimed compounds allow their efficient utilization as an active media for liquid lasers, day light fluorescent dyes and in other industries.
The second aspect of the present invention includes an improved process for preparing key intermediates in the manufacture of compounds of formula I. These improved methods include a process for preparing a compound of the formula (II): 
wherein R is hydrogen or alkyl having from 1 to 4 carbon atoms.
A purpose of the invention is to develop new chemical colorants in the benzothioxanthone series with red fluorescence and improved solubility in organic solvents, a longer spectrum in the red region and higher light stability. The second goal is a better method of making the 2-oxybenzanthrone product that will increase yield of transitional and final products under more favorable manufacturing conditions.
This problem is solved by development of new benzothioxanthone colorants with the generic formula I: 
wherein R1 is a straight chain alkyl group having from 6 to 22 carbon;
R2, R3 and R4 are each, independently, hydrogen or alkyl having from 1 to 4 carbon atoms.
The compounds have improved solubility.
Particularly useful compounds described above include those where R2, R3 and R4 of the formula I are hydrogen, particularly valuable compounds where R1 is a straight chain octyl group. A particularly valuable dye of the present invention is 6-n-octyloxy-14H-anthra(2,1,9-mna)thioxanthene-14-one.
The compounds of formula I may be prepared by known methods or by the improved process of the invention.
By way of illustration, the following schematic diagram shows a method of making of one of the claimed components the 6-n-octyloxy-14H-anthra(2,1,9-mna)thio xanthene-14-one. 
Generally, a 2-oxybenzanthrone may be alkylated with an alkyl halide in the presence of sodium or potassium carbonate in a polar-aprotic solvent to provide the desired 2-alkoxy compound. Bromination of the alkoxy compound with n-bromo succinimide in the presence of glacial acetic acid provides the neighboring 3-bromo substituent, which is then reacted with ortho-amino thiophenol at reflux in a polar-aprotic solvent such as, for example, dimethylformamide (DMF). The product is then ring-closed by treatment with hydrochloric acid, followed by reaction with sodium nitrite and then addition of a copper sulfate catalyst.
The above-described synthesis of the compounds of the present invention employs 2-oxybenzanthrones as intermediate materials.
The present invention also includes the process for manufacturing 2-oxybenzanthrones of the formula (II): 
wherein R is hydrogen or alkyl having from 1 to 4 carbon atoms, comprising:
(a) reacting a compound of the formula III 
xe2x80x83with an alkali metal nitrite in the presence of an acid to form a diazonium acid salt;
(b) reacting the diazonium salt with isopropenyl acetate and a catalytic amount of a cuprous halide (I) in a solvent to form a compound of the formula (IV): 
and
(c) reacting the compound of the formula of step (b) with a base in an alcohol solvent at the reflux temperature of the solvent; subsequently adding a sufficient amount of acid to render the pH between about 4 and 5 and collecting the desired compound.
According to the invention, the reaction described in step (b) of the diazonium salt with isopropenyl acetate and a catalytic amount of a cuprous halide is conducted in a mixture of acetonitrile and water in 1:1 ratio.
In particular, the improvement is achieved in the synthesis of the compound with formula (V) 
wherein R is hydrogen or alkyl having 1 to 4 carbon atoms and including the reaction of the formula (VI): 
wherein X is a residue of sulfuric or hydrochloric acid with isopropenyl acetate and a catalytic amount of cuprous halide in a mixture of acetonitrile and water solution in a 1:1 volume ratio.
In step (a), the preferred acid is concentrated sulfuric acid which forms the diazonium sulfate salt; however hydrochloric or hydrobromic acid may be used, resulting in the formation of a diazonium halide salt. In step (c), the preferred base is an alkali metal hydroxide, for example, sodium or potassium hydroxide.
The compounds of the present invention are useful as red color fluorescent dyes.
Objects and advantages of the invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in the examples, as well as other conditions and details, should not be construed to unduly limit the invention. All parts, percentages and ratios herein are by weight unless otherwise specified.